The method for determining the content of phosphoric acid in the sample was as follows: We took a 0.5 g sample and placed it in a beaker, added 1.0 mL of concentrated sulfuric acid and 1.0 mL of concentrated nitric acid successively, and heated it until white smoke was produced. After the solution was cooled, we added 1.0 mL of 30% H2O2 and heated it again. We repeated the above operation until no white smoke was generated. Then, we added 1.0 mL of 6 mol/L hydrochloric acid and heated it to decompose the residual acid in the solution. Taking 5.0 mL of P-ACP solution, the content of phosphoric acid in the sample was determined by drawing the standard curve.
Phosphoric acid content = (0.2175 A − 0.0075)/S × 100% formula, where A is the absorbance of the sample measured at 660 nm, and S is the mass (g) of the sample.
Phosphoric acid content = (0.2175 A − 0.0075)/S × 100% formula, where A is the absorbance of the sample measured at 660 nm, and S is the mass (g) of the sample.
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